Microscope Guide: Compound or Stereo?

Whether to buy a compound or stereo microscope is a question frequently asked of us here at PeplerOptics.
Both are considered optical microscopes (often called light microscopes) but are otherwise quite different.

Compound Microscope (Biological) – High power
These microscopes are designed for observation at high magnification from 40x to 1000x. and are ideal to examine biological samples such as blood samples, bacteria, water organisms, etc.

Stereo Microscope – Low power
Stereo Microscopes are designed for examination at relative low magnifications from 4.5x to 200x times. A three-dimensional image and large depth of focus make them ideal for viewing more substantial specimens such as insects, leaves, gems, etc. as well as being very popular in industrial inspection.

Both types have two sources of magnification. One through the objective lens and the second through the eyepiece. The total magnification is achieved by multiplying the magnification of the objective lens by that of the eyepiece lens.

For example a magnification of 1000x can be achieved using a standard eyepiece magnification of 10x with a 100x objective lens.
Choosing a microscope usually starts with selecting either a Biological or Stereo Microscope depending on your application and the magnification needed.

Choosing a Compound Microscope (Biological)

These microscopes are designed for observation at high magnification from 40x to 1000x.
Most laboratory or research grade microscopes are equipped with objective lenses giving up to 600x or 1000x total magnification but for hobby or home use up to 400x magnification is usually sufficient. A typical compound microscope will have 3, 4 or 5 objective lenses offering 40x, 100x, 400x, and either 600x or 1000x.

Compound microscopes come with either a monoocular head (one eyepiece), binocular (two eyepiece) or trinocular (with a third, trinocular port).

Monocular microscopes are easy to use for young children and are the lowest cost.

Binocular microscopes are more comfortable to use and may come with a mechanical stage allowing to move the specimen inspected smoothly.

Trinocular microscopes are slightly more expensive but allow to add a digital camera (optional), giving you the possibility to save images and view them on a computer. Adding a camera makes these microscopes particularly engaging for children.

In addition, a few monocular models exist with a digital camera integrated into the head. These offer an attractive package price with the limitation that the camera cannot be upgraded later.

Other features to consider are a mechanical stage for moving the slide under examination and LED illumination.

Choosing a Stereo Microscope

Stereo microscopes are designed for observation at relative low magnifications from 6.5x x 55x but can be expanded up to 200x.

They are constructed with either a fixed or adjustable magnification (zoom) objective.

Stereo microscopes consist of two distinct optical paths providing 2 images, one for each eye. The human brain combines the two images into one 3-dimensional image with increased depth of focus.

Stereo microscopes are used extensively in industry, education and by hobbyists. They are ideal for inspection and examination in areas such as watchmaking, jewellery, circuit board manufacture, entomology (insects), botany, geology, etc.

These microscopes come with either a binocular or trinocular head. The latter is provided for attaching a digital camera to capture images (camera is optional).

In addition, a few models exist with a digital camera integrated into the head. These offer an attractive package price with the limitation that the camera cannot be upgraded later.

Illumination is always required. Some models such as those with pillar or rack and pinion stands have illumination built in as standard.

We recommend selecting a boom stand for applications needing a larger working area such as PCB inspection. For these boom stands, illumination needs to be added as an accessory.

Go Digital

Both compound or stereo microscopes maybe fitted with a digital camera for viewing and saving images on a computer. However, there is another alternative in the form of purely digital microscopes where the use is always with a computer without any eyepieces. These are becoming more and more the go to choice for low power applications and there are some great products available from entry level hand-held digital microscopes to high end professional inspection & measurement systems such as the Inspex II from Ash Technologies.